why don't you try shaving a bit off of one of the cubes of frozen bloodworms? I have tried that and it works fairly well. once you pop the cube out of the package and shave (use steak/paring knife) off the bit to defrost, just wrap the rest of the cube up in saranwrap (i double wrap mine) until the next time you need it. sometimes i'll put the wrapped cube in a little container just to make sure no yuckies get in it from the freezer (i'm not as picky with my freezer being clean as i am with the fish tanks... lol) just make sure to wash hands good prior and after, so no yuckies get on food and in case you have allergy to bloodworms.
As for what i feed my bettas: each of the four get a couple Hikari Betta BioGold pellets in the morning with two or three little (i crumble them a bit) freeze dried blood worms. evening they get a few thawed frozen bloodworms and either a couple freeze dried bloodworms or one or two pellets. sounds like a lot but all four are quite active and i never have problems with bloated bellys, constipation, or swim bladder. the myth that bettas are lazy is totally unfounded. people only think they are lazy because they usually don't have room to swim in the little "torture bowls", therefore they don't swim.
And bettas are not picky eaters. i've only had my new female home for two days and she is already eating whatever is served to her, although she did have to eyeball the frozen worm for a minute, then gulp! and they are all housed in seperate tanks, so no competition for food. Bettas are not picky, my other female will even try to eat the little plastic stick i use to put the worms in the tank! lol.